Cynical I am maybe, but I give high odds on a harassment operation meant to make the Bummer government look good (and BATFE may have even said the time was not ripe for such a raid and gotten overruled), rather than any “smoking gun” (pardon the pun) having been found blaming the fellow for genuine wrongdoing.
Maybe they were so busy watching him that they had no time to catch all those walked guns before they went to Mexico. Yeah that’s the ticket.
I think I see a pattern forming.